@@ -197,8 +197,12 @@ if (TI_WITH_LLVM)
 
     check_clang_version()
 
-    if (${CLANG_VERSION_MAJOR} VERSION_GREATER ${CLANG_HIGHEST_VERSION})
-      message(FATAL_ERROR "${CLANG_EXECUTABLE} version: ${CLANG_VERSION}, required: <=${CLANG_HIGHEST_VERSION}. Consider passing -DCLANG_EXECUTABLE=/path/to/clang to cmake to use a specific clang.")
+    if(${CLANG_VERSION_MAJOR} STREQUAL "")
+        # Do nothing
+    else()
+        if (${CLANG_VERSION_MAJOR} VERSION_GREATER ${CLANG_HIGHEST_VERSION})
+          message(FATAL_ERROR "${CLANG_EXECUTABLE} version: ${CLANG_VERSION}, required: <=${CLANG_HIGHEST_VERSION}. Consider passing -DCLANG_EXECUTABLE=/path/to/clang to cmake to use a specific clang.")
+        endif()
     endif()
 
     add_subdirectory(taichi/runtime/llvm/runtime_module)